An amplifying circuit that amplifies a differential signal is used in a semiconductor device. The amplifying circuit includes two metal oxide semiconductor (MOS) transistors that have substantially the same characteristics and form a differential pair. Substantially identical loads are coupled between respective drains of the two MOS transistors and one power terminal. Sources of the two MOS transistors are indirectly or directly coupled to the other power terminal. Thus, a symmetrical differential pair is generated. When differential signals are applied to respective gates of the two MOS transistors, differential outputs are obtained from the respective drains of the two MOS transistors. The two MOS transistors may be coupled to each other at their sources, and a common load may be coupled between a connection node of the sources and the other power terminal. A differential circuit may or may not include a common load. A differential amplifying circuit may include an amplifying circuit that amplifies a differential signal.
Related art is disclosed, for example, in Japanese Laid-open Patent Publication Nos. 2009-094570, 2010-068165, and 2005-160026.